"Harriet" the PortMiami Tunnel boring machine breaks through Dodge Island after completing the first of two tunnel tubes from Watson Island. (Source: CBS4)

MIAMI (CBSMiami) – Construction of the new $1 billion PortMiami tunnel reached a milestone Tuesday when “Harriet”, the giant tunnel boring machine digging under Government Cut, reached the halfway point.

“This project is about the future, it’s about the Port, it’s about cargo, it’s about crews, and it’s about making this happen for people here in Miami-Dade,” said Miami Access Tunnel project manager Chris Hodgkins.

Harriet broke through Dodge Island Tuesday, after traveling 4,200 feet under Government Cut to create the first of two tunnel chambers.

“It’s something huge, it’s something unique and really puts us on the map as an international city, as a progressive city,” said Maggie Fernandez of the Miami-Dade Office of Sustainability.

Crews officially broke ground on the project two years ago, but digging on the eastbound tunnel didn’t start until November 2011.

As Harriet moves forward, it erects precast concrete liners, known as segments, which become the finished wall of the tunnel.

Once the liners are in place, grout is pumped into the space between it and the excavated area to fill any voids or gaps.

The completed tunnel will consist of two tubes featuring two lanes each.

The bottom of the tunnels will be approximately 120 feet below the surface of Government Cut at their deepest point.

Once completed, 1.5 million trucks a year are expected to travel through the tunnel that will connect Watson Island and PortMiami between Government Cut, the main shipping channel in Biscayne Bay.

“They are talking about our PortTunnel in China and they talking about our business in Brazil,” said Miami-Dade County Mayor Carlos Gimenez.

The Port’s goal is to double cargo capacity over the next decade and bring in big business.

In the meantime, the project has created more than 6,000 local jobs so far.

For construction worker Anthony Daniel, it means the promise of a job for the next two years.

“It makes me feel great. Job security and everything and like I said it’s here for the community.”

Now that Harriet has arrived at the Port, the machine; which is as high a 4-story building and longer than a football field, will be partly disassembled, turned around and re-assembled for the trip back to Watson Island that will create the second tunnel chamber in the westbound direction.

The project is expected to be completed in May 2014.

The PortMiami Tunnel project is a public-private partnership between Miami Access Tunnel, FDOT, Miami-Dade County and the City of Miami.